This research proposal is concerned with the auditory and phonetic stages of processing which constitute the first analysis of the speech signal. A number of experimental procedures, including selective adaptation, detection, reaction time and recognition masking will be used in conjunction with synthetic speech and complex nonspeech sounds to study perceptual stages and limitations within an information processing framework. Experiments will examine the potential role of feature detectors in mediating auditory and phonetic processing, the role of contextual information in phonetic processing and the contrast between dynamic and steady-state information at all stages of speech processing. These experiments will help to distinguish between general auditory processes and specialized processes in speech perception. The experimental data will also be used to elaborate and refine an information processing model of speech perception that has been implemented as a computer simulation. The simulation will allow precise, quantitative tests of the model and facilitate comparison with other models of speech perception.